(1) Field of the Invention
The present invention relates to an electric wire sizing-cutting apparatus for use in a manufacturing process of a wiring harness and specifically, to an electric wire sizing-cutting apparatus, in which an electric wire wound onto a reel is delivered by an electric wire delivery apparatus, a bending habit of the electric wire is corrected, and the electric wire is cut into a predetermined length.
(2) Description of the Related Art
A motor vehicle as a mobile unit mounts various electronic instruments. Therefore, the motor vehicle mounts a wiring harness, which transmits electric power from a power supply and control signals from a computer to the electronic instruments. The wiring harness includes a plurality of electric wires and connectors attached to ends of the electric wires.
The electric wire includes a core wire (electrical conductor) formed by twisting a plurality of element wires made of metal together and a coating made of electrically insulating synthetic resin, which coats the core wire. The connector includes a terminal fitting and a connector housing receiving the terminal fitting. The terminal fitting is made of conductive sheet metal and attached to an end of the electric wire so as to be electrically connected to the core wire of the electric wire. The connector housing is made of insulating synthetic resin and formed in a box-shape.
In the wiring harness, when the connector housing is connected to the electronic instrument, each electric wire is electrically connected to the electronic instrument through the terminal fitting so as to transmit electric power and signals to the electronic instrument.
When the wiring harness is being assembled, first, a long electric wire wound onto a reel is sized up and cut into a predetermined length and thereafter, the coating of an end part of the electric wire is removed and a terminal fitting is attached thereto. Thereafter, the terminal fitting is inserted into the connector housing. Thus, the wiring harness is assembled.
FIG. 5 shows an electric wire sizing-cutting apparatus (for example, see Japanese Patent Application Laid-Open No. 2005-011706) having a conventional electric wire delivery apparatus, by which a long electric wire wound onto a reel is sized up and cut into a predetermined length, in a process for manufacturing the wiring harness.
The electric wire sizing-cutting apparatus 100 shown in FIG. 5 includes: an electric wire reel 102 winding a long electric wire 112 thereonto; a transfer device 105 transferring the electric wire 112 wound onto the reel 102 in the longitudinal direction of the electric wire 112; a correcting device 104 correcting a bending habit of the electric wire 112 by passing the electric wire 112 into between the rollers 143, 144 each arranged zigzag; a hook 103 holding the electric wire 112 movable and arranged between the correcting device 104 and the reel 102; a joint detecting part 106 detecting a joint portion of the electric wire 112 wound onto the reel 102; an encoder 107 measuring a transfer amount of the electric wire 112; a cutting device 108 cutting the electric wire 112 into a predetermined length on the basis of the transfer amount of the electric wire 112 detected by the encoder 107; a control device 109 controlling the driving of the transfer device 105, joint detecting part 106 and encoder 107; and a frame 110 fixing the hook 103, correcting device 104, transfer device 105, detecting part 106 and encoder 107 and placed on a floor in a plant. The electric wire reel 102, hook 103, correcting device 104 and transfer device 105 constitute a electric wire delivery apparatus 114.
The electric wire reel 102 includes: a body part 123 formed in a column-shape and winding the electric wire 112 onto an outer peripheral surface thereof; a round cover part 122 attached on an upper surface of the body part 123; and a plurality of bearded needles 124 arranged radially from an outer edge of the cover part 122. The bearded needle 124 prevents the electric wire 112 from being delivered from the reel 102 by inertia when the movement of the electric wire 112 is stopped. That is, the bearded needle 124 functions as a back tension upon delivering of the electric wire 112. The bearded needle 124 prevents the electric wire 112 from excessively being delivered from the reel 102 so as to prevent a slack of the electric wire 112 from occurring between the reel 102 and the hook 103.
The electric wire 112 wound onto the reel 102 is a coated electric wire having an insulating coating on an outer circumference of the core wire, which is formed by winding up a plurality of element wires twisted spirally. The electric wire 112 wound onto the reel 102 forms a long electric wire 112 by bonding the core wires of a plurality of the electric wires together. In this specification, a portion at which the electric wires 112 are bonded together is called a joint portion. When a slack of the electric wire 112 takes place between the reel 102 and the hook 103, the electric wire 112 does not smoothly move on the hook 103 due to a bending habit of the electric wire 112, wherein the bending habit is provided to the electric wire 112 by being wound onto the reel 102. Therefore, the bearded needles 124 are arranged radially from the outer edge of the cover part 122 so as to prevent a slack of the electric wire 112 from occurring.
The hook 103 is attached to an end of the frame 110 near the reel 102, the height of the end being about the same as that of the correcting device 104. The hook 103 serves to supply the electric wire 112 delivered from the reel 102 to the correcting device 104 positioned at the downstream side, in a straight manner without being entangled.
The correcting device 104 includes a first correcting device 141 and a second correcting device 142 lined up along a transfer direction K of the electric wire 112. The first correcting device 141 has a plurality of rollers 143 lined up zigzag and arranged in a direction in which an axial direction of each roller 143 is parallel to a horizontal direction. The second correcting device 142 has a plurality of rollers 144 lined up zigzag and arranged in a direction in which an axial direction of each roller 144 is parallel to a vertical direction. When the electric wire 112 passes through the first and second correcting devices constructed as described above, a bending habit of the electric wire 112 is corrected and the electric wire 112 is extended straight.
The joint detecting part 106 includes a pair of rollers and a power supply (not shown in the figure) for applying a voltage to the rollers. When the core wire of the electric wire 112 passes through between the pair of the rollers with contacting the rollers, a current flows between the pair of the rollers, so that a joint portion of the electric wire 112 is detected.
Recently, the electric wire 112 for use in a wiring harness tends to be thin. When a thin electric wire 112 including a core wire having a cross sectional area of 0.13 mm2 is used for the electric wire sizing-cutting apparatus 100 shown in FIG. 5, there is a problem that a kink takes place at a portion located between the electric wire reel 102 and the hook 103. Here, the kink means that a twisted electric wire 112 is deformed in a C-shape by being excessively pulled. When the kink takes place, a coating of a portion deformed in a C-shape becomes white, causing deterioration in mechanical strength of the coating.
A cause of the kink formation is that the electric wire 112 is rotated along an axial direction thereof when the electric wire 112 passes through between the rollers 143 and between the rollers 144 of the correcting device 104. In detail, since the core wire of the electric wire 112 is formed by being twisted spirally, the rollers 143 and the rollers 144 come in contact with the electric wire 112 in such a manner that the rollers 143 and the rollers 144 move along spiral grooves of the core wire through the coating, and the electric wire 112 is rotated because the electric wire 112 is successively conveyed. Then, the twist occurred due to the rotation of the electric wire 112 is stored at a portion located between the electric wire reel 102 and the hook 103. Although the electric wire 112 is prevented to some extent from slackening by the bearded needles 124, when an amount of the twist increases, the bearded needles 124 cannot control the twist any more, causing that a kink takes place at the portion described above when the electric wire 112 is delivered from the reel 102.
When the kink described above takes place at an intermediate portion of the long electric wire 112, the driving of the electric wire sizing-cutting apparatus 100 must be halted for a while so as to cut the electric wire 112 to remove the pertinent portion of the electric wire 112 before the driving is restarted, causing deterioration in productivity.
As for a conventional electric wire 112, a twist takes place when the electric wire 112 wound onto the reel 102 is pulled in an axial direction thereof by the rollers 143 and 144 of the correcting device 104. However, the electric wire 112 is rotated in a direction reverse to the twist upon passing through between the rollers 143 and 144, so that the twist is absorbed and thereby preventing a kink from occurring at a portion where the twist takes place by being pulled by the correcting device 104 on a condition that the twist takes place. When the electric wire 112 is thick, such a kink tends to hardly take place.
A method of preventing the kink from occurring, in which the rollers 143 and 144 are suitably replaced according to a pitch of twisting of the core wire of the electric wire 112, has been proposed. In this case, it is necessary to frequently replace the rollers 143 and 144, causing deterioration in productivity or a problem that the driving of the electric wire sizing-cutting apparatus 100 is performed without replacing the rollers 143 and 144.